ent-pimara-8(14), 15-dien-19-oic acid isolated from the roots of Aralia cordata inhibits induction of inflammatory mediators by blocking NF-κB activation and mitogen-activated protein kinase pathways

Macrophages play central roles in the innate immune system. The roots of Aralia cordata are widely used in Oriental medicine as a remedy for arthritis. During our program to screen medicinal plants for potential anti-inflammatory compounds, ent-pimara-8(14), 15-dien-19-oic acid (pimaradienoic acid; PA) was isolated from the roots of A. cordata. We examined the effect of PA on pro-inflammatory mediators in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages. PA was found to significantly inhibit the production of nitric oxide (NO), prostaglandin E₂ (PGE₂), and interleukin-6 (IL-6), as well as the expressions of inducible NO synthase (iNOS), cyclooxygenase-2 (COX-2), and IL-6. Furthermore, we examined whether mitogen-activated protein kinases (MAPKs) and phosphatidylinositol 3-kinase (PI3K) signaling pathways are involved in LPS-induced RAW 264.7 cells. We found that a p38 inhibitor (SB203580) and an ERK 1/2 inhibitor (PD98059) significantly affected LPS-induced IL-6 production. In contrast, a JNK 1/2 inhibitor (SP600125) and PI3K inhibitor (wortmannin or LY294002) did not block the induction of IL-6 production by LPS. The LPS-induced phosphorylation of p38 MAPK and extracellular signal-regulated kinase 1/2 (ERK1/2) was inhibited by PA, but not the phosphorylation of JNK 1/2 and AKT (Ser473). Moreover, PA suppressed IκBα degradation, NF-κB activation and luciferase activity. These results suggest that PA isolated from A. cordata has a potential regulatory effect on inflammatory iNOS, COX-2 and IL-6 expression through blockade of the phosphorylation of MAPKs following IκBα degradation and NF-κB activation.